In recent years, a foam core sandwich panel is used as a structural material for an aircraft body, rapid-transit rail car, and the like. This foam core sandwich panel is of a structure in which a surface layer, also referred to as a face plate, made of fiber reinforced plastic (abbreviated as FRP) is integrally formed on the surface of a core layer made of a foam synthetic resin material. The foam core sandwich panel has many advantages in that it is light in weight, gives high stiffness, prevents the intrusion of liquid such as water, and is moldable in one piece to reduce parts in number, but presents a problem that it is susceptible to delamination between the surface layer and the core layer.
Conventional art for preventing the delamination between the surface layer and the core layer is proposed, for example, in Japanese Laid-Open Patent Application Publication No. 2006-282046. This prior art proposes to provide an arrester between a face plate forming the surface layer and a core material forming the core layer to retard the progression of a crack by this arrester and prevent the delamination between the face plate and the core material.